题解 | 电商平台需要对商家的销售业绩、退款情况和客户满意度进行综合评估

select
    merchant_id,
    merchant_name,
    total_sales_amount,
    total_refund_amount,
    average_satisfaction_score
from
    merchants_underline
    join (
        select
            merchant_id,
            sum(refund_amount) as total_refund_amount
        from
            refunds_underline
        group by
            merchant_id
    ) t1 using (merchant_id)
    join (
        select
            merchant_id,
            round(avg(satisfaction_score), 2) as average_satisfaction_score
        from
            satisfaction_underline
        group by
            merchant_id
    ) t2 using (merchant_id)
    join (
        select
            merchant_id,
            sum(sale_amount) as total_sales_amount
        from
            sales_underline
        group by
            merchant_id
    ) t3 using (merchant_id)
group by
    merchant_id,
    merchant_name
order by merchant_id asc